The long term objective of this project is the production of improved media for the preservation of anaerobic bacteria during transport of specimens from the patient to the clinical laboratory. The ability of Oxyrase (R), an oxygen-reducing enzyme system, to produce anaerobic conditions in transport media is evaluated. Sterile Oxyrase is added to three commonly used media and the survival of test organisms is compared to survival in the same media containing sodium thioglycollate or cysteine. These agents are frequently used to achieve anaerobic conditions. The media is challenged over a period of several days by the introduction of small amounts of air. Samples are removed for quantitative enumeration of living bacteria. After conditions that optimize the performance of the Oxyrase system are established, the ability of media to preserve anaerobes in the presence of aerobic and facultative bacteria is evaluated. The shelf-life at different temperatures of Oxyrase-containing transport media is also determined. Finally, the Oxyrase transport media is tested in a clinical laboratory for their ability to preserve a large group of anaerobes in the presence and absence of facultative and aerobic bacteria.